Recently, global warming comes into problem with the increase of carbon dioxide emission, and the suppression of CO2 emission becomes an important issue in the iron industry. In recent blast furnaces is used lump coke charged from a top portion of the furnace and pulverized coal blown through tuyeres as a reducing material. The use of pulverized coal blown through the tuyeres into the furnace is considered to easily lead to the suppression of CO2 emission as compared to the use of the lump coke charged from the top of the furnace in view of the difference in the carbon dioxide emission generated by a pretreatment for suppressing CO2 emission.
In general, as to the blowing of the pulverized coal through the tuyeres, Patent Document 1 discloses that pulverized coal containing a volatile matter of not more than 25 mass % is blown at a rate of not less than 150 kg/t per 1 ton of pig iron as a pulverized coal ratio. In this case, it is attempted to improve combustion efficiency by feeding oxygen of not less than 70 vol % through a lance together with the pulverized coal for preventing the decrease in the combustion efficiency of the pulverized coal. Further, Patent Document 1 proposes a method wherein when the lance is a single tube, a mixture of oxygen and pulverized coal is blown from the lance, while when the lance is a double tube, the pulverized coal is blown from an inner tube and oxygen is blown from between an inner tube and an outer tube.
Patent Document 2 proposes a method wherein when the combustion efficiency is decreased at the pulverized coal ratio of not less than 150 kg/t−p during the production cutback (tapping ratio of not more than 1.8), a high-volatile pulverized coal containing a volatile matter of not less than 28 mass % is used and a heat flow ratio represented by a ratio of solid heat volume to gas heat volume is controlled to not more than 0.8.